1. Field of the Invention
The present invention relates to a mobile terminal with a personal authentication function and a mobile terminal system. More specifically, the invention relates to a mobile terminal with a personal authentication function and a mobile terminal system, which prevent the unauthorized use of the mobile terminal by an unauthorized person when the mobile terminal is stolen or lost.
2. Description of the Related Art
In recent years, mobile terminals such as mobile phones and mobile devices have become more popular, and the easy-to-operate feature thereof has been improved drastically. On the other hand, such a mobile terminal is portable with no physical connection and, therefore, likely to be stolen or lost. Hence, there is a possibility that the stolen or lost mobile terminal is possessed and used by an unauthorized person against the will of the owner of the mobile terminal.
For prevention of the unauthorized use by the unauthorized person, there is known a so-called mobile terminal locking technique, which disables some or all of the functions of the mobile terminal when the owner finds the mobile terminal missing (see, for example, Japanese Unexamined Patent Publication No. HEI 6(1994)-125305).
This technique makes it possible to remotely control the mobile terminal from a communication device other than the mobile terminal so as to lock the mobile terminal. This technique prevents the unauthorized use of the missing mobile terminal by the unauthorized person.
However, this technique is based on the presumption that action is taken after the owner finds the mobile terminal stolen or lost. Therefore, the unauthorized use of the mobile terminal by the unauthorized person cannot be prevented during a period from a time point at which the mobile terminal is lost to a time point at which the mobile terminal is found lost. That is, it is impossible to promptly take action.
To cope with this, a technique for promptly taking action against the unauthorized use has been developed (see, for example, Japanese Unexamined Patent Publication No. HEI 9(1997)-191342). FIG. 8 illustrates the construction of a mobile terminal system according to the prior art.
In this technique, a position registration terminal 32 for a mobile terminal 31 is preliminarily provided separately from the mobile terminal 31. The mobile terminal 31 and the position registration terminal 32 constantly transmit positional information to a communication base station 33. If a distance between the mobile terminal 31 and the position registration terminal 32 is greater than a predetermined distance, the communication base station 33 transmits information on this fact to the owner of the mobile terminal. This technique makes it possible to promptly detect the steal or loss of the mobile terminal. Upon reception of the information, the owner of the mobile terminal requests the communication base station to lock the mobile terminal, whereby the unauthorized use of the mobile terminal by an unauthorized person can be prevented.
Where the position registration terminal provided separately from the mobile terminal is carried together with the mobile terminal, however, the convenient portability feature is deteriorated. This is a great disadvantage in view of a recent major challenge to the size reduction and weight reduction of the mobile terminal.
Even if the position registration information from the mobile terminal and the position registration terminal is updated as frequently as possible in consideration of power consumption, the unauthorized use of the lost mobile terminal within the coverage of the same communication base station cannot be prevented.